Ice cream or frozen custard machines, as well as other systems for cooling or freezing food stuffs, condiments, or other materials, typically include an evaporator situated proximate the material being chilled. For example, in ice cream machines and soft serve machines, liquid ice cream (e.g., the mix) is typically inserted in a freezing chamber or barrel associated with the evaporator and is removed from the barrel as solid or semi-solid ice cream. The evaporator removes heat from the freezing chamber as a liquid refrigerant, such as, FREON®, ammonia, R-404a, HP62, or other liquid having a low boiling point, changes to vapor in response to the heat from the liquid ice cream. Typically, the evaporator is partially filled with vapor as the liquid refrigerant boils (e.g., becomes vapor) in the evaporator.
Quick freezing of liquid ice cream and high capacity are desirous features of ice cream makers. In addition, custard or ice cream quality and efficient manufacture of such custard or ice cream are dependent upon maintaining a constant evaporator temperature (e.g., constant barrel temperature). The barrel temperature must be kept in a proper range for making ice cream. If the custard or ice cream is allowed to become too cold, the mix or liquid ice cream in the evaporator becomes highly viscous and can block the travel of the ice cream through the barrel. Blockage of the barrel in the freezing process is commonly known as “freeze up”. If the ice cream or custard is allowed to become warm, its texture is adversely affected.
Maintaining the temperature of the barrel at a constant level is particularly difficult as ice cream flow rates through the machine vary and change the cooling load on the evaporator. For example, more heat dissipation is required as more ice cream is produced (i.e., the flow rate is increased). Additionally, if the barrel temperature is too low, refrigerant flood-back problems can adversely affect the operation of the compressor. For example, if the refrigerant is not fully evaporated as it reaches the compressor, the liquid refrigerant can damage the compressor.
Problems associated with temperature consistency are exacerbated during periods of non-production (e.g., an idle mode, a period of slow sales, a hold mode, etc.). Generally, ice cream machines, particularly soft serve machines, can experience non-production modes, periods of little or low production operation or a “hold” mode. During this mode, liquid ice cream and frozen ice cream product remain in the barrel (the cooling chamber) awaiting to be processed. However, due to the low demand for ice cream, ice cream is not removed from the barrel. The ice cream in the barrel can be subjected to temperature fluctuations during these periods of non-production due to heat infiltration.
Heretofore, ice cream machines have required that the refrigeration system (the compressor) be cycled on and off to maintain the ice cream in the barrel at the appropriate temperature. Such conventional systems have been unable to accurately maintain the barrel temperature at a proper and consistent temperature. For example, the fairly large compressors associated with the ice cream machine cool (e.g., overcool) the barrel down and then allow it to warm back up before the compressor is engaged to cool the barrel. The temperature within the barrel fluctuates according to a sawtooth wave. The gradual freezing and thawing causes the product to break down such that texture of the product becomes more grainy and less desirable to the taste.
Further, conventional systems have allowed the liquid ice cream mix to have constant access to the barrel. Generally, conventional systems have included a liquid ice cream reservoir connected to the evaporator via an aperture. The allowance of liquid ice cream to enter the barrel during non-production times contributes to the warming of the ice cream in the barrel, thereby affecting the quality of the ice cream within the barrel when liquid ice cream is allowed to fill the barrel, the liquid ice cream can become frozen against the barrel, thereby reducing the freezing efficiency of the barrel.
Further, conventional systems have allowed the ice cream product to be periodically and automatically mixed (i.e., beaten) in the evaporator during non-production modes or slow sales periods. Overbeating of the ice cream product results in poor ice cream texture and less desirable taste.
Thus, there is a need for an ice cream machine which can operate in a hold mode and not allow the barrel temperature to fluctuate drastically. Further still, there is a need for a process and a machine which can more efficiently and more evenly cool ice cream. Even further still, there is a need for a frozen machine which utilizes a barrel and maintains the ice cream product at a consistent temperature.
Yet even further still, there is a need for a process or method which does not allow liquid ice cream to affect the temperature in the barrel while in a hold or non-production mode. Yet even further, there is a need for an ice cream machine which does not allow the chamber wall to become coated with ice cream. Further still, there is a need for an evaporator and a control system for an ice cream machine which prevents breakdown of the ice cream product during slow sales periods. Further, there is a need for a hold mode for an ice cream machine which requires little or no bearing of the ice cream product.